New guy here with a 98 318ti also my first BMW . Been lurking trying to figure out how to navigate the forum so forgive me if this is in the wrong place for this post . Also trying to figure out how to post pictures from my libraries. Got a nice clean all stock example for cheap . It's has what seems to be all the common issues from what I've read. First thing is to sort is the cooling issue . Doesn't go past the half way point on the gage but when you start driving it goes to the blue and on these freezing days cool air coming out of the vents doesn't cut it . Next on list will be fixing the oil leaks . So hopefully I can figure out this site and use the wealth of knowledge of you 318 enthusiasts to good use.

Welcome, I'm also pretty new to the form. I had the same issue with mine when I first got it. First thing to do is to make sure you have coolant, there was a small leak in my system so coolant would be leaking out an I'm guessing the air in the system did not help. So I suppose that's two things, check for coolant and make sure you're not leaking any. Secondly, as 318tiFatherFigure said, it could be your thermostat, that seems like a common failure point for these cars. Replacing it wasn't too difficult, took me around 1-2 hours with putting in new coolant. I'd suggest going with the OEM 88C thermostat. As long as you're not overheating the engine, that's really a bigger pain than just driving with low/no heat.